This invention relates to a magnetic recording medium comprising a plastic base of polyester film or the like uniformly coated on one side with a dispersion of a ferromagnetic powder in a resin binder.
It is common knowledge with the manufacture of magnetic recording media, such as audio and video tapes and floppy discs, to reinforce the magnetic recording coat by the addition of a finely divided, nonmagnetic inorganic material so as to protect the coat against damage due to contact with the magnetic head of a recorder. However, unless the kind, particle size, and quantity of the nonmagnetic inorganic powder are properly chosen, the addition can impair or increase the abrasive wear of the head. Recently, especially with video cassette tapes, there has been increasing demand for greater wear resistance (better still characteristic) to cope with the spread of video tape recorders (VTRs) featuring such auxiliary functions as still and slow motion modes. On the other hand, the introduction of more and more high-performance video tapes has entailed a tendency to use finer ferromagnetic particles, a trend unfavorable for the still characteristic. As countermeasures, attempts have been made to harden the material of nonmagnetic inorganic particles or to increase the proportion of the powder to be added. Both attempts have, however, brought rather serious drawbacks such as increased wear of the head and shortened head life. We have studied on nonmagnetic inorganic materials which would lessen the impairment of the magnetic recording medium and reduce the wear of the head.